Train Carbody Research Articles

Reinforcement learning control of lateral vibration of high-speed train carbody

Abstract Increasing speed is one of the effective ways to raise high-speed train (HST) transportation capacity. However, increasing speed leads to greater vibration of HST with passive suspension, which can reduce the smoothness and safety of HST. Thus, a twin delayed deep deterministic policy gradient (TD3) control strategy was designed to reduce the lateral vibration of the HST carbody. The 3-degree-of-freedom (DOF) and 17-DOF models were utilized in designing the TD3 controller and simulation, respectively. In addition, the ballastless track spectrum of the Chinese high-speed railway was utilized to obtain the irregularities of the track. A reward function containing cost and penalty was designed to raise TD3 controller training efficiency. A linear quadratic optimal cost function and a step penalty function were designed, respectively. The control effect of the TD3 strategy was studied by simulation. The results indicate that TD3 can effectively reduce root-mean-square (RMS) and peak values for lateral acceleration at the front and rear ends of the HST carbody, and significantly improve the lateral smoothness of the HST carbody, which verifies validity of TD3 strategy.

Research on resonance mechanism of articulated train car body based on modal vibration extraction method

Research on resonance mechanism of articulated train car body based on modal vibration extraction method

An active suspension system for enhancing running safety of high-speed trains under strong crosswind

The running safety of trains subjected to strong crosswinds has become a major concern for the high-speed railways passing through complicated mountain areas. This paper reports an active secondary suspension system to improve the operation stability and running safety of high-speed trains under strong crosswind. The goal of the active suspension system is to regulate the lateral, yaw, and roll motion attitudes of high-speed train carbody, in which a controller is designed by combining with a disturbance observer and the sliding mode control method. To further verify the proposed active suspension strategy, a crosswind-vehicle-track coupled dynamics model is established, where the unsteady aerodynamic loads and random track irregularity excitations are considered. The results show that the proposed active suspension system has the efficient potential to regulate the carbody motion attitudes and enhance the anti-rolling performance of high-speed trains. In comparison to a quasi-static control strategy of active suspension, the use of the proposed active suspension system has led to a significant reduction in both wheel-load reduction ratios and derailment risks of high-speed trains.

Calibration and validation of fatigue design models for railway car bodies considering uncertainty

AbstractThe fatigue design of railway vehicles is a requirement for resource‐ and energy‐efficient lightweight design. A simulation‐based design process makes high demands on the reliability of results. Therefore, this work focuses on the calibration of weld quality parameters for the simulation‐based fatigue design of railway car bodies. Since the direct measurement of weld parameters is costly, an indirect Bayesian calibration approach is implemented, effectively combining limited testing with numerical simulations. Fatigue tests have been performed on the probe, component, and structure level for the load‐bearing section of the Next Generation Train (NGT) car body within the SimbaCon (Simulation‐based Conception) project at DLR. Based on the distribution of the measured life spans for component tests, the corresponding weld seam quality factors are calibrated using Bayesian calibration. The resulting weld seam qualities are used for the fatigue assessment of the complex car body structure.

Effect of the Laying Order of Core Layer Materials on the Sound-Insulation Performance of High-Speed Train Carbody.

The design of sound-insulation schemes requires the development of new materials and structures while also paying attention to their laying order. If the sound-insulation performance of the whole structure can be improved by simply changing the laying order of materials or structures, it will bring great advantages to the implementation of the scheme and cost control. This paper studies this problem. First, taking a simple sandwich composite plate as an example, a sound-insulation prediction model for composite structures was established. The influence of different material laying schemes on the overall sound-insulation characteristics was calculated and analyzed. Then, sound-insulation tests were conducted on different samples in the acoustic laboratory. The accuracy of the simulation model was verified through a comparative analysis of experimental results. Finally, based on the sound-insulation influence law of the sandwich panel core layer materials obtained from simulation analysis, the sound-insulation optimization design of the composite floor of a high-speed train was carried out. The results show that when the sound absorption material is concentrated in the middle, and the sound-insulation material is sandwiched from both sides of the laying scheme, it represents a better effect on medium-frequency sound-insulation performance. When this method is applied to the sound-insulation optimization of a high-speed train carbody, the sound-insulation performance of the middle and low-frequency band of 125-315 Hz can be improved by 1-3 dB, and the overall weighted sound reduction index can be improved by 0.9 dB without changing the type, thickness or weight of the core layer materials.

A Review of Recent Research into the Causes and Control of Noise during High-Speed Train Movement

Since the invention of the train, the problem of train noise has been a constraint on the development of trains. With increases in train speed, the main noise from high-speed trains has changed from rolling noise to aerodynamic noise, and the noise level and noise frequency range have also changed significantly. This paper provides a comprehensive overview of recent advances in the development of high-speed train noise. Firstly, the train noise composition is summarized; next, the main research methods for train noise, which include real high-speed train noise tests, wind tunnel tests, and numerical simulations, are reviewed and discussed. We also discuss the current methods of noise reduction for trains and summarize the progress in current research and the limitations of train body panels and railroad sound barrier technology. Finally, the article introduces the development and potential future applications of acoustic metamaterials and proposes application scenarios of acoustic metamaterials for the specific needs of railroad sound barriers and train car bodies. This synopsis provides a useful platform for researchers and engineers to cope with problems of future high-speed rail noise in the future.

Mechanism of high-speed train carbody shaking due to degradation of wheel-rail contact geometry

ABSTRACT The carbody shaking phenomenon (CSP) can greatly reduce the ride comfort of high-speed trains. To investigate the abnormal vibration feature and causes of the CSP, extensive field measurements and numerical simulations were conducted. A three-dimensional rigid-flexible coupled dynamic model of a high-speed vehicle is constructed to reproduce the CSP and reveal the key influence factors, in which the finite element model of the carbody is updated based on the experimental modal data. The field test show that the main vibration frequency of the carbody accelerations appear around 7.90 Hz, which is close to the natural frequency of the carbody diamond mode. The simulation results demonstrate that the CSP is caused by the carbody resonance vibrations induced by bogie hunting motion, which is triggered by the deterioration of wheel-rail contact geometry. When the train passes through turnouts at high speed, wheel-rail impact will further aggravate the CSPs.

Optimization of an EMU train carbody by the value of the natural bending frequency

Finding ways to optimize the body structure is an important point in the design of new electric train cars. Reducing the mass of the body leads to a lightening of the parts of the rolling stock associated with it, a reduction in energy consumption for operation and a decrease in wear in the “wheel — rail”system. Reducing the weight of the body is possible by assigning optimal rigidity to its main load-bearing elements. Increasing the rigidity of the body with a constant mass is also an important task to obtain the standard dynamic properties of the car body.The article presents method for optimizing the body structure based on calculating the value of its first frequency of natural bending vibrations. The calculation was carried out by the finite element method using a simplified beam-shell parametric model. Within the optimization calculations, 3125 working versions of sections of the main load-bearing structural elements with different rigidity were considered — bracing and cross-beams of the frame, inter-window racks and cross-beams of the roof. The sensitivity of the value of the natural vibration frequency to the change in the rigidity of the main bearing elements without taking into account the change in mass is analyzed. It was found that the rigidity of the frame bracing and cross beams has the greatest influence on the frequency value. It is shown that the ratio of the rigidity of the main bearing elements does not remain constant for optimal design options and depends on the design of the body, the target values of its mass and rigidity. When mass is limited, it is possible to choose designs that are characterized by the greatest overall body rigidity and are the most optimal in terms of manufacturability. By limiting the values of natural vibration frequency, it is possible to choose a body structure with the lowest metal mass. The presented approach allows making decisions on body modification based on the required parameters of mass and (or) the frequency of natural bending vibrations. This approach can be used in pre-design studies of the bodies of new passenger rolling stock.

Temperature- and frequency-dependent vibroacoustic response of aluminium extrusions damped with viscoelastic materials

Viscoelastic materials are commonly used as damping materials for noise and vibration control in composite structures. However, their effective damping temperature range is usually extremely narrow, and a comprehensive understanding of their temperature- and frequency-dependent properties is lacking. Therefore, in this study, we analyse the temperature- and frequency-dependent vibroacoustic response of aluminium extrusions damped with viscoelastic materials. First, three kinds of modified butyl rubbers with the best damping performance at different temperatures were fabricated. Their glass transition temperatures were measured using differential scanning calorimetry, and their temperature- and frequency-dependent damping loss factors and elastic moduli were determined through dynamic mechanical analyses and using the time–temperature equivalence rule. Subsequently, to practically apply the viscoelastic materials to a high-speed train carbody, the heat transfer characteristics of aluminium extrusions were analysed using the finite element method, and the vibroacoustic behaviours of the composite structure were investigated considering the temperature- and frequency-dependent damping loss factors and elastic moduli of the viscoelastic materials. Finally, the key parameters of the viscoelastic materials that affect the radiated sound power of the composite structure were discussed, and multilayer damped aluminium extrusions using three different viscoelastic materials were analysed. The results demonstrate that in order to control the noise and vibration of composite structures over a wide range of temperatures, not only the temperature range and damping performance of viscoelastic materials should be broadened and improved, respectively, but also the damping loss factor and elastic modulus should be matched considering temperature and frequency variations.

Response based track profile estimation using observable train models with numerical and experimental validations

Condition monitoring of railway tracks is essential in guaranteeing the running safety of railways. Track profiles are the primary source of external excitation for a train system. While Track Recording Vehicle is often utilized for maintenance purposes, this particular vehicle is expensive and difficult to use for small railway operators. Therefore, track profile estimation through in-service vehicle response measurements, which potentially provides efficient and frequent measurement, has been studied. However, the quantitative evaluation of the vertical and lateral track profile irregularities is still challenging as the inverse analysis solutions are sometimes inaccurate and even unstable. In this paper, numerical analyses are first carried out to evaluate track profiles from acceleration and angular velocity responses measured on a train car body. For the inverse analysis, an Augmented State Kalman Filter is utilized to solve the problem using 4 degrees of freedom observable train models. The sensor installation locations are investigated through observability rank condition analysis with different measurement layout. Secondly, a field experiment is carried out in a local Japanese in-service railway network to estimate track profile from car body motions. Smartphones are utilized for the field test measurements as prevalent sensing devices. The effectiveness of the proposed approach is demonstrated with the observable train model. Numerical analyses and field experiments clarify the proposed track profile estimation

A boundary-condition-transfer method for shell-to-solid submodeling and its application in high-speed trains

The boundary-condition-transfer method for a shell-to-solid submodeling is fundamental for analyzing local or weak regions of a complex structure accurately. In this paper, a novel method is presented for transferring displacement boundaries based on hypothetical nodes. By considering the invariable volume of an element as a constraint, the interpolation through conventional methods using 6-degrees-of-freedom (DOFs) nodal translations and rotations is converted into a 3-DOF translational interpolation at the cut boundary of a submodel. To demonstrate this method, a radial basis function (RBF) was employed for interpolation. For validating the accuracy of the proposed method, a square plate with a hole under tensile and bending load were designed as examples. By considering global and local errors, three typical kernel functions with respect to mesh density ratios were analyzed to fix the optimal parameter in RBF. The examples showed that the proposed method significantly improves the accuracy in shell-to-solid submodeling problems compared to conventional solutions such as ANSYS. For structural analysis of a high-speed train car body under combined mechanical and aerodynamic loads, the submodeling method was implemented on the solid-element-based local model with a welding seam, with which a more detailed stress state was obtained compared with that computed by shell elements. The accurate and reliable results illustrate that the proposed method is the core for the global–local analysis of large complex structures, which also is used for the design and evaluation of the mechanical properties.

Investigating the feasibility of a new testing method for GFRP/polymer foam sandwich composites used in railway passenger vehicles

This paper investigates the feasibility and validity of a recently proposed testing method when applied to foam core sandwich composites to determine the impact resistance of train car body shells. The published method proved itself useful when applied to monolithic fibre reinforced plastic laminates, however, further analysis is required if sandwich composites are used due to the subtle differences compared to monolithic laminates. It is especially important for the front nose section of high-speed trains as these car body parts can be subjected to ballast flight at high impact velocities. Due to the aerodynamic design aspects, front nose sections generally incorporate complex 3D geometries, and sandwich composite materials are advantageous in this respect due to the ease of manufacturing of complex 3D shapes. Quasi-static punch tests (QSPT) were performed on E-glass fibre/epoxy resin/PET foam core sandwich plates. Numerical finite element model (FEM) was developed and validated with experiments in terms of penetration resistance and structural damage. Numerical model was used to investigate three railway impact related standards and high-velocity impact parameters (energy transfer, contact force, projectile velocity) were analysed for each case. Additionally, the foreseeable contribution of this work to the railway industry was given from multiple aspects.

On the damage mechanism of high-speed ballast impact and compression after impact for CFRP laminates

Single and multiple track-ballast impacts are investigated for the CFRP laminates used in train carbodies. Numerical simulations have been performed to study the damage behaviors of CFRP laminates during ballast impacts and compressions after ballast impact (CABI). Intralaminar and interlaminar damages are successfully predicted using continuum damage mechanics and cohesive zone model, respectively. It reveals that, for a high-speed ballast impact, delamination occurs during the damage initiation and appears at several interfaces nearby the impacted side of the specimen. After that, fiber breakage and matrix cracking appear, while delamination continuously extends until the failure. Repeated ballast impacts on the same site and different sites of specimens show significant increase of delamination while indicating less intralaminar damage. Furthermore, CABI simulations show that, the residual compression strength decreases in a nonlinear manner with the increase of impact energy. To bear the same impact energy, less detrimental effect is caused when one impact is replaced by two or more impacts.

The coupled effects of bending and torsional flexural modes of a high-speed train car body on its vertical ride quality

This study is focused on the effects of bending and torsional flexural modes of the car body on the ride quality index of a high-speed train vehicle. The Euler–Bernoulli beam model is used to extract an analytical model for a high-speed train vehicle car body in order to investigate its bending and torsional flexural vibrations. The rigid model includes a car body, two bogie frames, and four wheelsets such that, each mass has three degrees of freedom including vertical displacement, pitch motion, and roll motion. The results obtained with the proposed analytical model are compared with experimental measurements of the car body response of a Shinkansen high-speed train. Moreover, it is determined that the bending and torsional flexural modes have significant effects on the vertical acceleration of the car body, particularly in the 9–15 Hz frequency range. Furthermore, the ride quality index is calculated according to the EN 12299 standard and it is shown that the faster the train the more affected is the ride quality by the flexural modes. In addition, the effect of coherence between two rail irregularities (the right and the left rails) on the results of the simulation is investigated. The results conclude that if the irregularities are completely correlated the torsional flexural mode of the car body does not appear in the response. Also, the first bending flexural mode in such cases is more excited compared with the partially correlated or uncorrelated rail irregularities. Therefore, the ride quality index in completely correlated cases is higher than other cases.

Experimental characterisation and modelling of intra‐car communications inside high‐speed trains

The rising demand of high-capacity wireless services on-board has driven the research interest on radio communications in public transportation systems. In this experimental study, the authors focus on the intra-car communication links in a high-speed train (HST), which have been rarely reported in the literatures. Specifically, the authors have carefully measured and modelled the radio propagation characteristics for intra-train link. Measurements at both 2.4 and 5.8 GHz have shown that propagation losses inside the train car are much lower than free space, where path-loss exponent increases as the receiver moves away from the transmitter. Otherwise, the shielding loss and frequency dependent penetration losses caused by the train car body shell are parameterised. In addition, the small-scale fading is also evaluated to formulate a complete propagation model for intra-car communications. This work aims to support the Internet access for passengers,for onboard sensor networks and broadband moving-relay solutions.

A Practical Structural Health Monitoring System for High-Speed Train Car-Body

A practical structural health monitoring (SHM) system based on Lamb wave for high-speed train car-body structures is presented. The system can detect the occurrence and report the location and probabilistic size of structural damage in real-time. Based on the theory of Lamb wave, a piezoelectric transducer array network is implemented to generate and acquire the detection signal by mounting on the surface of the structure to be monitored. An algorithm, that can locate, quantify and image the damage based on the damage index that indicates the differential between baseline signal and current acquired signal, is proposed to develop the system. Furthermore, a system framework of three-layer architecture and a diagnosis strategy are designed to build the SHM system. Finally, the system is implemented on China's latest high-speed train (CRH380A) operated along the Chengdu-Chongqing High-Speed Railway after well tuning then demonstrates the feasibility and reliable in practical application.

Lean Manufacturing Approach to Reduce Wastefulness During Production of Train Car-Body Using VALSAT Method

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Influence of equipment rigidity on the natural bending frequency of the EMU train car body

The first frequency of the own bending vibrations of the car body of the EMU train is one of the main normalized parameters associated with smooth running. Estimation of this parameter at the design stage allows to accelerate the process of development of design documentation and to reduce further number of tests. Rigidity of the undercarriage and roof equipment of the EMU train cars contributes to the overall rigidity of the body. When simulating the equipment with concentrated masses at the attachment points, underestimating the rigidity of the body results in underestimated values of the first natural frequency of bending vibrations of the body. It is shown that modeling the equipment with a rigid area with subordinate nodes at the attachment points makes it possible to simplify the process of constructing the model and adequately take into account the rigidity of the equipment not only in determining the static characteristics of body deflections, but also in calculating the dynamic characteristic and the first natural frequency. Using subordinate nodes of a rigid area on the surfaces of the fixing holes leads to a reassessment of the natural frequency. Value of the first natural frequency of the body oscillations is linearly dependent on the specific weight of the undercarriage equipment. When designing the bodies of EMU train cars (especially motor cars), in order to increase the frequency value, the equipment boxes should be located, taking into account the compatibility of the deformations of the box frames and the loadbearing structure of the body. Massive boxes for small equipment should be placed as close to the bolster beams as possible. If it is necessary to place largesize boxes under the car equipment, one should consider variants of its location in the central part of the body to include the box frames in the bend of the transverse beams of the frame.

Analysis on the Acoustic Contribution of the High Speed Train Car Body Panels

High speed train interior structural noise which caused by vibration of car body panels influence passengers ride comfort directly. The car body panels’ acoustic contribution analysis can determine the location of the panels which affect considerably the interior structural noise. Then that modifying the car body panels with a clear aim can improve the vibration characteristics of car body panels to reduce the interior noise. Using acoustic transfer vector method, the car body panels’ acoustic contribution of the high speed EMU were analyzed to determine the location of the panels which affect considerably the interior noise.

Effect of train carbody’s parameters on vertical bending stiffness performance

Finite element analysis(FEA) and modal test are main methods to give the first-order vertical bending vibration frequency of train carbody at present, but they are inefficiency and waste plenty of time. Based on Timoshenko beam theory, the bending deformation, moment of inertia and shear deformation are considered. Carbody is divided into some parts with the same length, and it’s stiffness is calculated with series principle, it’s cross section area, moment of inertia and shear shape coefficient is equivalent by segment length, and the fimal corrected first-order vertical bending vibration frequency analytical formula is deduced. There are 6 simple carbodies and 1 real carbody as examples to test the formula, all analysis frequencies are very close to their FEA frequencies, and especially for the real carbody, the error between analysis and experiment frequency is 0.75%. Based on the analytic formula, sensitivity analysis of the real carbody’s design parameters is done, and some main parameters are found. The series principle of carbody stiffness is introduced into Timoshenko beam theory to deduce a formula, which can estimate the first-order vertical bending vibration frequency of carbody quickly without traditional FEA method and provide a reference to design engineers.